Using Inheritance to Promote Marriage Within the Faith

Hello readers…this is one in which I'm really interested in hearing your comments.

Religion Clause reports that the Illinois Supreme Court upheld a clause in someone's will that an inheritance would go to those of his grandchildren that "married within the Jewish faith." Four of his five grandchildren married Gentiles, and got nothing. One of them contested the will, arguing among other things, that it violated due process and free exercise clauses of the Constitution. The Supreme Court upheld the will.

I'm not so interested in the specific legal issues, as I am in the concept. Is this a good and proper way to encourage endogamy (in-marriage)? Would you put a clause like this in your will? Why, or why not?